1. Department of Soil Sciences; SLU; Box 7014 750 07 Uppsala Sweden
2. Department of Microbiology; SLU; Box 7025 750 07 Uppsala Sweden
3. Sida, Dusjanbe (DHL); 105 25 Stockholm Sweden
4. Institute of Terrestrial Ecology; ETH Zürich; CH-8952 Schlieren/Zürich Switzerland